In TMP Kirk has been an Admiral for several years, I forgot his exact position I know he tells Scotty it in the pod scene, and his post has been an earth bound one for the most part.
So V'ger comes along, the not yet finished refit Enterprise is the only ship in range of course (Think about that. This means there were exactly ZERO fully operational starships around or near earth!!! Wow, not exactly a strong defense if the Klingons decided to attack)
Kirk convinces his superior he needs to be captain of the Enterprise, despite the ship's new design, because of his experience in these situations vs. Decker's lack of it. So when he tells Decker he's assuming command he also informs he being temporarily demoted to commander, with the assumption he'll be re promoted to captain and take over the Enterprise once the V'ger thing is over.
My question is why would Decker need to be demoted? The knee jerk answer is "Well a ship can't have two captains" but that's irrelevant because:
1. Kirk is a higher rank to begin with so by regulations Decker would have to obey his orders. Whether he was a captain or commander in rank made no difference.
2. Captain is an official rank, but it is also the title given to any commanding officer of a ship in the military. In the navy a ships skipper may only be a commander rank wise but he is referred to as captain when commanding the ship.
So it's not the rank but the command that determines a person's authority. Even if Decker remained a captain in rank he was no longer captain of the Enterprise. While Kirk despite being an Admiral could be referred to captain, in reference to his position of commanding the ship.
Even if Kirk had had to take a demotion to captain because starfleet had some regulation about flag officers not commanding individual ships, and Decker remained a captain it wouldn't have made them equal in authority because starfleet had designated Kirk as the commanding officer of the Enterprise. So even they would have both been captains rank wise only Kirk could be called "captain" of the Enterprise and Decker by regulations would have been bound to follow Kirk's orders.
So it made no sense to have to demote Decker to make Kirk's command of the Enterprise seem more official. I think the writers just threw it in there to make Decker even more pissed at Kirk that not only did he take command of the Enterprise away from him, but he lost his official rank as well.
So V'ger comes along, the not yet finished refit Enterprise is the only ship in range of course (Think about that. This means there were exactly ZERO fully operational starships around or near earth!!! Wow, not exactly a strong defense if the Klingons decided to attack)
Kirk convinces his superior he needs to be captain of the Enterprise, despite the ship's new design, because of his experience in these situations vs. Decker's lack of it. So when he tells Decker he's assuming command he also informs he being temporarily demoted to commander, with the assumption he'll be re promoted to captain and take over the Enterprise once the V'ger thing is over.
My question is why would Decker need to be demoted? The knee jerk answer is "Well a ship can't have two captains" but that's irrelevant because:
1. Kirk is a higher rank to begin with so by regulations Decker would have to obey his orders. Whether he was a captain or commander in rank made no difference.
2. Captain is an official rank, but it is also the title given to any commanding officer of a ship in the military. In the navy a ships skipper may only be a commander rank wise but he is referred to as captain when commanding the ship.
So it's not the rank but the command that determines a person's authority. Even if Decker remained a captain in rank he was no longer captain of the Enterprise. While Kirk despite being an Admiral could be referred to captain, in reference to his position of commanding the ship.
Even if Kirk had had to take a demotion to captain because starfleet had some regulation about flag officers not commanding individual ships, and Decker remained a captain it wouldn't have made them equal in authority because starfleet had designated Kirk as the commanding officer of the Enterprise. So even they would have both been captains rank wise only Kirk could be called "captain" of the Enterprise and Decker by regulations would have been bound to follow Kirk's orders.
So it made no sense to have to demote Decker to make Kirk's command of the Enterprise seem more official. I think the writers just threw it in there to make Decker even more pissed at Kirk that not only did he take command of the Enterprise away from him, but he lost his official rank as well.